Here's a trivia question a local math teacher has been using to torture the high school junior class. Winner gets 20 extra credit points for the semester. The standard linear equation "y=Mx+B" was developed by Descartes, a French mathematician. The question is .... Why was the letter "M" chosen to represent slope & why was "B" chosen to represent the y-intercept? I believe the answer to the first part is "monter" or "to climb" ... a derivative of the french word for rise (slope). I can't guess the history of the "B".